Wind Turbines on the Parapet

The new AVX400 turbine, which will be released publicly in the fall of 2006, embodies a number of breakthroughs that greatly improve the viability of wind on some urban and suburban buildings. Among the technical improvements, the blades of the turbines were designed to operate at relatively low speeds, which dramatically reduces noise and vibration from the turbines—a major deterrent to placing turbines on buildings. More significant, however, is AeroVironment’s discovery that on wide buildings, even if they are not especially tall, the wind intensifies as it crests the building’s façade and moves over the roof. “If you go to the edge and look over, you get this rush of wind,” notes Paul Glenney, AeroVironment’s director of energy initiatives. In the field, AeroVironment has measured a 40% boost in wind speed, which translates into about 2.7 times as much energy in the wind.

While developing these technical advances, AeroVironment didn’t neglect the aesthetic and even psychological aspects of the problem. The turbine installation was designed for high visibility, acknowledging the fact that many building owners are proud of their onsite renewable energy systems and want to be able to show them off. In a similar vein, the company is working on getting the turbine to start spinning at wind speeds as low as 4 miles per hour (mph; 2 m/s), whereas 6 to 8 mph (3 to 4 m/s) is more typical for small turbines, and the AVX400 currently starts at 7 mph (3 m/s). The AVX400 doesn’t generate much power at that speed, but it communicates to observers that something is happening, which helps to generate interest and a positive reaction.